1. Field of the Invention
This invention relates generally to reflectors, and particularly to a color varying reflector, i.e. a reflector which returns different colors of light depending on whether the source is on one side or the other of a center line or plane passing through the reflector.
It has long been recognized that there would be a use for such reflectors. There are obvious applications in, for example, highway and airport traffic control. There are many situations in which it is useful to use a light source and such a reflector to receive an indication as to whether one is on one side or the other of a center line or plane. Combining reflectors in different locations may also permit specific locations to be identified, through triangulation techniques. Reflectors may be mounted on a post, or embedded at road, runway or taxiway level, or positioned in any other suitable manner.
2. Description of the Prior Art
In the prior art, numerous attempts have been made to produce reflectors which return different signals to the source depending on the position of the source. In the simplest case, reflector units have been constructed consisting of differently colored reflectors on front and rear faces, thus reflecting different colors to sources opposed at 180 degrees to each other from the reflector. Such reflectors have been used, for example, to provide a red reflection from headlights of highway traffic approaching the reflectors from one direction and a green reflection to traffic approaching from the other direction. Such reflectors obviously cannot make fine angular distinctions, however, such as between sources of light which may be separated by as little as 45 degrees or less, for example.
Other attempts in the prior art have employed means such as blinders projecting from the reflective surfaces towards the source, to shade one portion or another of the reflective elements depending on the angular position of the light source. The effectiveness of such units is obviously limited by the distance to which the blinders project from the reflectors, and such projections are susceptible to damage.
It is an object of the present invention to provide a color varying reflector which is relatively simple and effective, and which offers advantages over color varying reflectors in the prior art.